1. Field of the Invention
The present invention relates to a display unit which enables observation of a magnified image by one eye. The present invention relates also to a display unit which enables switching between image magnification modes: a non-magnification mode for observation of an image with two eyes (binocular observation) at a distance longer than the distinct vision distance, and a magnification mode for observation of the image with one eye (monocular observation) at a distance shorter than the near point of vision.
2. Related Background Art
Head mount displays (hereinafter referred to as xe2x80x9cHMDxe2x80x9d) are used for observation of a magnified image with one eye. However, such a display requires a large optical space for the image magnification for observation, and are not useful for non-magnified image observation with both eyes from a usual long distance. FIG. 1 shows a display unit disclosed in Japanese Patent Application Laid-Open No. 10-170860. This apparatus has a smaller optical space. In FIG. 1, the numerals and the symbols denote the following: 2, an ocular-side microlens array (pitch 70.8 xcexcm); 3, a transmission-type liquid crystal display element (pitch 76.3 xcexcm); 41, a light-condensing microlens array (pitch 81.8 xcexcm); 42, a light-parallelizing microlens array (pitch 90 xcexcm); 5, a flat backlight; 8, a diffusion hole sheet having apertures 9 serving as fine light spots (pitch 98.2 xcexcm); E, an eyeball of an observer; and O, the pupil of the eyeball. In FIG. 1, microlenses R and S correspond to pixels P and Q, respectively. In FIG. 1, the dimensions of the parts of the display unit are as follows: A=18.85 mm, B=20.3 mm, C21.77 mm, F23.95 mm, G26.13 mm, H=3 mm, D=3 mm, J=2 mm, K=2 mm, and M=25.9 mm. This display unit has an ocular optical system including microlenses for introducing the light beams emitted from the respective pixels. This display unit is provided to increase the light efficiency as the HMD by decreasing the thickness, but is not suitable at all for observation of an image with both eyes from a distant position. Specifically, as shown in FIG. 1, with the unit in which microlenses 2 are placed at the front side of liquid display element 3, when the image is observed with both eyes from a distant position, the visual axes of the both eyes intersect each other by convergence at the display element face (display face). However, the virtual image is formed apart from the element face by lens action of the microlenses 2. Therefore, the observed image is doubled. Accordingly, the displayed image cannot be observed in a favorable state from a position distant from the display face. Moreover, the microlenses are decentered from the pixels, which may cause cross-talk owing to the light from the adjacent aperture to lower the image quality. Further, Moire may be caused between the boundary of the microlenses and the boundary of the pixels of the display elements to lower the picture image quality.
FIG. 2 shows a display unit disclosed in U.S. Pat. No. 5,499,138. In FIG. 2, E denotes an eyeball; the numeral 81 denotes a field lens; 82, microlenses; and 83, an image displaying device. This display unit, which is capable of displaying an image compactly with high resolution as an HMD, does not enable observation from a distant position owing to the employed field lens. Even if the field lens is made detachable, Moire can be caused between the boundary of the microlenses and the boundary of the pixels owing to the arrangement of the microlenses as a part of the ocular optical system on the front side of the display elements, which makes the unit not suitable for binocular observation from a distant position.
As described above, the inventors of the present invention noticed the problem that conventional observation means for observing a magnified virtual image cannot be suitable for image observation from a distant point.
The present invention intends to provide a display unit which enables magnified image observation with one eye from a short distance, and which can be reduced in weight and thickness thereof. The present invention intends also to provide a display unit which enables magnified image observation with one eye at a short distance as well as non-magnified image observation with two eyes from a long distance.
The present invention provides a display unit comprising image displaying means having pixels arranged two-dimensionally, plate-shaped illumination means having fine light-emitting points arranged two-dimensionally corresponding to the pixels of the image displaying means and being placed on the backside of the image displaying means, and fine optical elements for introducing light emitted from the fine light-emitting points arranged two-dimensionally corresponding to the pixels of the image displaying means to the respective pixels. The pixels and the fine optical element and the fine light-emitting point corresponding to the pixels are arranged so that optical axes (the light beams passing through the respective optical centers) connecting the respective fine light-emitting points and the respective fine optical elements corresponding thereto pass through the pixels corresponding to the fine optical elements and the fine light-emitting points and intercross (intersect) substantially at a prescribed point within a distance of near point of vision of an eye from the display face of the image display means. Also, the fine optical elements form a virtual image of the fine light-emitting points corresponding thereto at a distance longer than a distinct vision distance of the eye from the prescribed point. The average eye has the near point of vision of 80 to 100 mm and the distinct vision distance of 250 mm. Therefore, in a general-purpose display, the distance between the aforementioned display face and the prescribed position is set at about 5 to 50 mm, and the distance between the prescribed position and the virtual image of the fine light-emitting point is set in the range from 250 mm to infinity, preferably at about 1 to 5 m.
A conventional display unit for observation of a magnified virtual image like the aforementioned HMD has an ocular optical system on an observer side of the display face for the virtual image observation. The display unit of the present invention has fine optical elements and fine light-emitting points on the back side of the image displaying means to observe the magnified virtual images of the fine light-emitting points magnified by the fine optical elements through the image display means. In other words, the magnified virtual image of the fine light-emitting points is observed by employing the arrangement plane of the fine light-emitting points as the object plane. Thus, the present invention is based on an idea different in principle from the display units of the prior art. The display unit of the present invention does not employ the ocular optical system for forming a magnified virtual image, in order to enable reduction of the thickness and weight of the display unit.
In another embodiment of the display unit of the present invention, the plate-shaped illumination means is constituted of a surface light source, and a barrier means which switches the light transmission mode to a aperture mode in which the light of the surface light source through apertures arranged two-dimensionally corresponding to the pixels, or to an entire transmission mode.
In the aperture mode in which the light of the surface light source is allowed to pass through the apertures, the constitution is the same as the display unit of the first embodiment: the magnified image is displayed for observation from a position at a shorter distance than the near vision point from the display plane. On the other hand, in the entire transmission mode in which the barrier means allows the light of the surface light source through the entire face, the entire plane of the image display elements is illuminated to cancel the formation of the virtual image of the fine optical elements and to allow observation of the non-magnified object from a position in a distance longer than the distinct vision distance.
The present invention provides a reflecting display unit which enables monocular observation of a magnified image from a short distance as well as binocular observation of a non-magnified image from a long distance.
According to an aspect of the present invention, there is provided a display unit comprising image displaying means having pixels arranged two-dimensionally, plate-shaped illumination means having fine light-emitting points arranged two-dimensionally corresponding to the pixels and being placed on the backside of the image displaying means, and fine optical elements for introducing light emitted from the fine light-emitting points arranged two-dimensionally corresponding to the pixels, to the respective pixels. The pixels, and the fine optical elements and the fine light-emitting points corresponding to the pixels are arranged so that optical axes connecting the respective fine light-emitting points and the respective fine optical elements corresponding thereto pass through the pixels corresponding to the fine optical elements and the fine light-emitting points and the optical axes intercross (intersect) substantially at a prescribed point within a distance of a near point of vision of an eye from a display face of the image display means. Further, the fine optical elements form a virtual image of the fine light-emitting points corresponding thereto at a distance longer than a distinct vision distance of the eye from the prescribed point.
The above plate-shaped illumination means may comprise a surface light source, and a barrier means having apertures arranged two-dimensionally corresponding to the pixels and serving as the fine light-emitting points by transmitting the light from the surface light source.
The above barrier means may be capable of taking an aperture formation mode to allow the light of the surface light source to pass through the apertures, or an entire transmission mode, by switching.
According to another aspect of the present invention, there is provided a display method, employing the aforementioned display unit. The method enables monocular observation of magnified displayed information from the prescribed point or vicinity thereof by switching the barrier means to the aperture formation mode to allow the light of the surface light source to pass the apertures. The method also enables binocular observation of non-magnified information from a distance longer than distinct vision distance from the display face of the image display means by switching the barrier means to the entire transmission mode.
According to still another aspect of the present invention, there is provided a display instrument, employing the aforementioned display method.
According to a further aspect of the present invention, there is provided a display unit comprising a reflecting-type display element having a reflection face having pixels and apertures corresponding to the pixels for transmitting light beams, a surface light source placed on the back face of the display element, and microlenses arranged two-dimensionally in front of a display face of the display element corresponding to the pixels. The microlenses, the pixels and apertures corresponding respectively to the microlenses are arranged such that the optical axes connecting the corresponding microlens, pixel, and aperture intercross (intersect) at substantially one point at a magnified image observation position at a distance shorter than the near point of vision in the opposite side of the display element relative to the two-dimensionally arranged microlenses. Also, the microlenses form a magnified virtual image of the corresponding apertures at a distance longer than the distinct vision distance.
According to a further aspect of the present invention, there is provided a display method, employing the aforementioned display unit, which displays a magnified image by turning-on of the surface light source to be observed monocularly at or near the observation position, and displays a non-magnified image by turning off the surface light source to be observed at a position from a distance not shorter than distinct vision distance from the display face.
According to a further aspect of the present invention, there is provided a display instrument, employing the aforementioned display unit.
For achieving the above objects, the present invention provides a display unit which comprises reflecting display elements, apertures on the reflecting face of the display elements for transmitting light beams in correspondence with the pixels on the display elements, a surface light source placed on the back side of the display elements, and microlenses in front of the display face of the display elements in correspondence with the pixels. The pixels of the display element are arranged in two dimensions. Therefore, the apertures and the microlenses are arranged similarly in two dimensions. The microlenses, the pixels and apertures corresponding respectively to the microlenses are arranged such that the optical axes connecting the corresponding microlens and aperture intercross roughly at one point at the magnified image observation position at a distance shorter than the near point of vision on the side opposite to the display elements relative to the two-dimensionally arranged microlenses, and that the microlenses form a magnified virtual image of the corresponding apertures at a distance longer than the distinct vision distance.
The average eye has the near point of vision of 80 to 100 mm and the distinct vision distance of 250 mm. Therefore, in a general-purpose display unit, the distance between the microlenses and the magnified-image observation position is set at about 5 to 50 mm, the distance between the magnified-image observation position and the virtual image of the apertures is set in the range from 250 mm to infinity, preferably at about 1 to 5 m.
With the display unit of the present invention, the observer can observe a magnified virtual image of the apertures by peeping into the display face by bringing his pupil at or near the magnified image observation position on lighting of the surface light source; and the observer can observe the real-size of the displayed image on light-out of the surface light source from the observation position at a distance longer than the distinct vision distance. In this display unit, the microlenses are placed on the observation side of the display face, which is different from a usual reflecting display unit for real-size observation. However, the adverse effect of the microlens in the non-magnified image observation can be made negligible by adjusting the distance between the microlenses and the pixels sufficiently shorter than the distance between the microlenses and the apertures to bring the image magnification of the microlenses near to 1.
The present invention provides also a display unit which enables observation of a magnified virtual image of the pixel portion by peeping the pixels with one eye, having the pixel portion near the observer, the light source distant from the observer, and the magnifying optical system between the one eye of the observer and the light source to enable the observation of a non-magnified image of the pixels by looking at the pixel portion with two eyes.